Fuel injection control apparatus and method for a multi-fuel engine, and engine incorporating same

Abstract

A fuel injection control apparatus for a multi-fuel engine can optimize a fuel injection quantity, using only one basic injection map, irrespective of alcohol concentration of a fuel. An E-concentration determining apparatus determines alcohol concentration of a fuel, based on a measured oxygen amount in exhaust. Basic injection quantities are stored in a basic injection map. E-concentration coefficients are stored in an E-concentration coefficient table for a plurality of alcohol concentrations in the fuel. A basic injection quantity, corresponding to a current rotary engine speed and a throttle opening, is selected from the basic injection map. A concentration coefficient, corresponding to the alcohol concentration and the basic injection quantity, is selected from the E-concentration coefficient table. A fuel injection quantity calculator determines an applied fuel injection quantity by multiplying the basic injection quantity by the concentration coefficient. Further adjustments using a number of additional correction coefficients may be made, as needed.

1. A fuel injection control apparatus for a multi-fuel engine, which is configured to control an injection quantity of an alcohol-mix fuel to said engine based on a measured oxygen concentration in an exhaust gas, the fuel injection control apparatus comprising:
 an oxygen sensor which is configured to measure an oxygen concentration in the exhaust gas, and to output a signal corresponding to the measured oxygen concentration; 
 an alcohol concentration-determining apparatus which is configured to determine an alcohol concentration in the fuel, based on the measured oxygen concentration; 
 a basic injection map which is configured to set a basic injection quantity of the fuel for a plurality of operation states of the engine; said basic injection map being recorded on a recordable medium; 
 an alcohol concentration coefficient table which is configured to set an alcohol concentration coefficient for a plurality of combinations of the basic injection quantity of the fuel and the alcohol concentration of the fuel; said alcohol concentration coefficient table being recorded on a recordable medium; 
 an injection quantity selector which is configured to select a currently applicable basic injection quantity, corresponding to a current operation state of the engine, from the basic injection map; 
 an alcohol concentration coefficient selector, which is configured to select the alcohol concentration coefficient corresponding to the alcohol concentration of the fuel and the basic injection quantity of the fuel from the alcohol concentration coefficient table; and 
 an applied injection quantity calculator, which is configured to calculate an applied fuel injection quantity based on the basic injection quantity and the alcohol concentration coefficient. 
 
   
   
     2. A fuel injection control apparatus for a multi-fuel engine according to  claim 1 , wherein the alcohol concentration coefficient is set such that the smaller the basic injection quantity, the higher the alcohol concentration coefficient becomes. 
   
   
     3. A fuel injection control apparatus for a multi-fuel engine according to  claim 1 , wherein the alcohol concentration coefficient is set to a fixed value when the basic injection quantity is greater than or equal to a predetermined injection quantity. 
   
   
     4. A fuel injection control apparatus for a multi-fuel engine according to  claim 1 , wherein said basic injection map includes a substantially similar basic injection quantity of the fuel at a number of different points therein correlating specified engine rotary speeds and throttle openings. 
   
   
     5. A fuel injection control apparatus for a multi-fuel engine according to  claim 1 , wherein said current operation state of the engine includes parameters associated with a current rotary engine speed and a throttle opening. 
   
   
     6. A fuel injection control apparatus for a multi-fuel engine according to  claim 1 , wherein when an intermediate alcohol concentration coefficient corresponding to determination of the alcohol concentration is not yet registered in the alcohol concentration coefficient table, the said intermediate alcohol concentration coefficient is calculated by performing one of interpolation and extrapolation processing. 
   
   
     7. The fuel injection control apparatus for a multi-fuel engine according to  claim 1 , wherein the basic injection quantity is one of a set of reference basic injection quantities stored in the basic injection map that are empirically derived based on a particular alcohol concentration, and wherein the applied injection quantity calculator is configured to use the basic injection quantity regardless of whether the alcohol concentration actually determined by alcohol concentration-determining apparatus differs from the particular alcohol concentration. 
   
   
     8. A method of determining an applied injection quantity of an alcohol-gasoline fuel mixture for a multi-fuel engine, said method comprising the steps of:
 a) measuring an oxygen concentration in exhaust gas from said engine, and outputting a signal corresponding to the measured oxygen concentration; 
 b) determining an alcohol concentration in the fuel, based on the measured oxygen concentration; 
 c) selecting a currently applicable basic injection quantity, corresponding to a current operation state of the engine, from a basic injection map; 
 d) selecting an alcohol concentration coefficient corresponding to the measured alcohol concentration in the fuel and the selected basic injection quantity of the fuel; and 
 e) calculating the applied injection quantity based on the selected basic injection quantity and the selected alcohol concentration coefficient. 
 
   
   
     9. A method of determining an applied injection quantity for a multi-fuel engine according to  claim 8 , wherein the alcohol concentration coefficient is set such that the smaller the basic injection quantity, the higher the alcohol concentration coefficient becomes. 
   
   
     10. A method of determining an applied injection quantity for a multi-fuel engine according to  claim 8 , wherein the alcohol concentration coefficient is set to a fixed value when the basic injection quantity is equal to or greater than a predetermined injection quantity. 
   
   
     11. A method of determining an applied injection quantity for a multi-fuel engine according to  claim 8 , further comprising a step of:
 f) opening a fuel injector solenoid valve for a predetermined time corresponding to the applied injection quantity calculated in step e). 
 
   
   
     12. A method of determining an applied injection quantity for a multi-fuel engine according to  claim 8 , wherein said basic injection map includes a substantially similar basic injection quantity of the fuel at a number of different points therein correlating engine rotary speeds and throttle openings. 
   
   
     13. A method of determining an applied injection quantity for a multi-fuel engine according to  claim 8 , wherein said current operation state of the engine includes parameters associated with a current rotary engine speed and a throttle opening. 
   
   
     14. A method of determining an applied injection quantity for a multi-fuel engine according to  claim 8 , wherein when an intermediate alcohol concentration coefficient corresponding to determination of the alcohol concentration is not yet registered in the alcohol concentration coefficient table, the said intermediate alcohol concentration coefficient is calculated by performing one of interpolation and extrapolation processing. 
   
   
     15. The method of determining an applied injection quantity for a multi-fuel engine according to  claim 8 , wherein the basic injection quantity is one of a set of reference basic injection quantities stored in the basic injection map that are empirically derived based on a particular alcohol concentration, and wherein the applied injection quantity is calculated using the basic injection quantity regardless of whether the alcohol concentration actually determined differs from the particular alcohol concentration. 
   
   
     16. In combination a multi-fuel engine and a fuel injection control apparatus for said multi-fuel engine, said fuel injection control apparatus comprising:
 an oxygen sensor which for measuring an oxygen concentration in the exhaust gas, and to output a signal corresponding to the measured oxygen concentration; said oxygen sensor being arranged in an exhaust pipe between said engine and a three-way catalyst disposed at a downstream side of the exhaust pipe; 
 an alcohol concentration-determining apparatus for determining an alcohol concentration in the fuel, based on the measured oxygen concentration; 
 a basic injection map for setting a basic injection quantity of the fuel for a plurality of operation states of the engine; said basic injection map being recorded on a recordable medium; 
 an alcohol concentration coefficient table for setting an alcohol concentration coefficient for a plurality of combinations of the basic injection quantity of the fuel and the alcohol concentration of the fuel; said alcohol concentration coefficient table being recorded on a recordable medium 
 an injection quantity selector for selecting a currently applicable basic injection quantity, corresponding to a current operation state of the engine, from the basic injection map; 
 an alcohol concentration coefficient selector for selecting the alcohol concentration coefficient corresponding to the alcohol concentration of the fuel and the basic injection quantity of the fuel from the alcohol concentration coefficient table; and 
 an applied injection quantity calculator for calculating an applied fuel injection quantity based on the basic injection quantity and the alcohol concentration coefficient. 
 
   
   
     17. A multi-fuel engine according to  claim 16 , wherein the alcohol concentration coefficient is set such that the smaller the basic injection quantity, the higher the alcohol concentration coefficient becomes. 
   
   
     18. A multi-fuel engine according to  claim 16 , wherein the alcohol concentration coefficient is set to a fixed value when the basic injection quantity is greater than or equal to a predetermined injection quantity. 
   
   
     19. A multi-fuel engine according to  claim 16 , wherein said current operation state of the engine includes parameters associated with a current rotary engine speed and a throttle opening. 
   
   
     20. The multi-fuel engine according to  claim 16 , wherein the basic injection quantity is one of a set of reference basic injection quantities stored in the basic injection map that are empirically derived based on a particular alcohol concentration, and wherein the applied injection quantity calculator is configured to use the basic injection quantity regardless of whether the alcohol concentration actually determined by alcohol concentration-determining apparatus differs from the particular alcohol concentration.